310 



MICRO-CHEMICAL RESEARCHES ON THE DIGESTION OP STARCH, &c. 



[1855. 



tity of lime contained in the bread is small — 100 ounces of lime require 

 more than 300 quarts of water for solution ; the lime contained in the 

 bread is scarcely as much as that contained in the seeds of leguminous 

 plants. Professor Liebig remarks that "it may be regarded as a 

 physiological truth, established by experiment, that corn flour is not a 

 perfectly alimentary substance ; administered alone, in the state of 

 bread, it does not suffice for sustaining life. From all that we know, 

 this insuificiency is owing to the want of lime, so necessary for the 

 formation of the osseous system. The phosphoric acid likewise re- 

 quired is sufficiently represented in the corn, but lime is less abundant 

 in it than in leguminous plants. This circumstance gives, perhaps, the 

 key to many of the diseases which are observed among prisoners, as 

 well as among children whose diet consists essentially of bread. * * 

 The yield of bread from flour kneaded with lime-water is more consi- 

 derable. In my household, 19 pounds of flour, treated without lime- 

 water, rarely give more than 24} pounds of bread ; kneaded with 5 

 quarts of lime-water, the same quantity of flour produces from 26 

 pounds 6 ounces to 26 pounds 10 ounces of well baked bread. Now as, 

 according to Heeren, 19 pounds of flour furnish only 24 pounds 1 J 

 ounces of bread, it may be admitted that the lime-water bread has un- 

 dergone' a real augmentation." — Annalen der Chemie und Pharmacie, 

 and Chemist, March, 1855. 



PUotogi'aiiliy. — Einploymcixt of tlie Cyauicl of loiliiic*-'" 



M. Stephane Geoffray, Advocate at Roanne, and a great amateur in 

 the art of photographj', has employed with success the cyanid of iodine 

 as the sensitive agent in direct positives. This compound he obtains 

 by the action of iodine upon cyanid of mercury. It is very soluble in 

 a solution prepared with wax and benzine, and gives to this coating a 

 rapidity of action nearly equal to that obtained by the use of ceroleinc. 

 jlpplied to collodion in the proportion of other iodids, the cyanid uni- 

 formly affords direct positive proofs of great beauty and which do not 

 subsequently change. After fixation in the old bath of hyposulphite, 

 the lights become very beautiful and are not inferior to those given by 

 the use of the sesquichlorid of mercury. 



M. Geoffray also employs the sesquichlorid of iron for all the pur- 

 poses for which the sesquichlorid of mercury has been hitherto used, 

 to brinf out negative proofs on collodion and upon albumen in the 

 manner employed for direct positives. He also employs this agent in 

 place of the iodid to prepare sensitive papers for making positives in 

 the shade .and in a few seconds ; according to the process of M. Blan- 

 quart-Ewrard. With this chlorid he also prepares a dry collodion of 

 excellent quality, as follows : 



To 100 grammes of ordinary non-sensitive collodion he adds 50 cen- 

 tin-rammes of dry and finely pulverized perchlorid of iron, having no 

 acid reaction ; he boils it for a quarter of an hour, and adds four drops 

 of tincture of iodine and filters the mixture. The glass being perfectly 

 cleaned, he pours on the collodion, waits a moment to allow the coat- 

 ing to acquire a certain solidity — then plunges it in a bath of nitrate 

 of silver, again in distilled water, and finally is dried, protected from 

 the dust. The image is revealed as usual by pyrogallic acid. 



This collodion is more sensitive than that prepared by using the 

 protochloi-ids, but is much less so than the moist collodions. 



Micro-cUcmical HcsearcUes on tlic Digestion of StarcU aiisl 

 Amylaceous Foods. 



BY PHILIP BURNAIID AYKES, M.D. LONDON.* 



Artificial AlcoIioI«'== 



In my last communication I neglected to speak of the production of 

 alcohol by means of water and illuminating gas. M. Berthelot has 

 reached this important result through a species of contact between C4 

 Hi dissolved in fuming sulphuric acid and water contained in the acid. 

 This important discovery has been the subject of a P^epoi-t to the Aca- 

 demy of Sciences by M. Thenard. In this Report (a very flattering 

 one to the young- chemist) the venerable Dean of French chemists 

 points out several other attempts of M. Berthelot and among them that 

 of converting grape sug.ar into cane sugar. In spite of certain diffi- 

 culties, we may still believe this a possible result. Nevertheless JM. 

 Biot doubts the possibility of this change, because it requires that the 

 intimate molecular structure of the substance should be changed, a 

 change to which we have no analogy in the transformations hitherto 

 made known. This difficulty however does not appear to MM. The- 

 nard and Dumas as insurmountable ; since in treating cane sugar, 

 with an acid, its molecular constitution is changed so'that its rotatory 

 power over the polarized ray is reversed from right to left, why then 

 should it be impossible to convert left-handed rotation to right-handed ? 



^American .Journal of Science. 



After some general historical remarks on the methods hitherto eiu- 

 ployed in the investigation of the complicated pha;nomena of the pro- 

 cess of digestion, the comparatively small results obtained by chemi- 

 cal analysis of the contents of the stomach, intestinal canal, and of the 

 evacuations, by Tiedemann and Gmelin, Berzelius, and others, the au- 

 thor proceeded to demonstrate the necessity of a minute examination 

 of the contents of the alimentary canal by the microscope, and such 

 chemical tests as we possess for the determination of the changes of 

 such articles of food as exhibit definite structure. 



In oi-der that we may ultimately arrive at a complete exposition of 

 the phajnomena of digestion, he is of opinion that it will be necessary 

 to examine, — first, the structure of particular kinds of food, then the 

 changes produced in them by cooking, and lastly to trace the changes 

 they undergo at short intervals, through the alimentai'y canal from the 

 stomach to the rectum. The results of a series of researches of this 

 character on the changes in starch, and starch-containing foods, are 

 presented in this memoir. |^ 



The method adopted for the examination of the changes in starch 

 and starch-foods was as follows : — An animal was kept fasting twenty- 

 four hours, and afterwards confined to a diet consisting of the starch 

 or amylaceous food, with water, for five or six days, until the debris 

 of all other kinds of food previously taken were cleared from the ali- 

 mentary canal. At a determinate time, after a meal, the animal wag 

 killed, the abdomen laid open as quickly as possible, and ligatures 

 placed at short intervals on the intestinal canal, from the pylorus to 

 the rectum. The contents of the stomach and each portion of the in- 

 testinal canal included between the ligatures were then carefully ex- 

 amined. This mode of examination sufiiced to determine the changes 

 which occur in the food during normal digestion ; but other questions 

 as to the particular secretion or secretions by which the changes ob- 

 served were effected. 



The fluids poured into the alimentary canal are five in number, — 

 the saliva, gastric juice, bile, pancreatic juice, and finally, the intes- 

 tinal mucus. 



The influence of the saliva is easily determined, by chewing the par- 

 ticular food subjected to experiment, and keeping the mixture at about 

 98° Fahr. The combined action of the saliva and gastric juice is seen 

 in the contents of the stomach. To determine the action of the biie, 

 the comjnon bile-duct was tied, and to ascertain the action of the in- 

 testinal mucus, it was necessary to ligature the bile and pancreatic 

 ducts. If the digestion of the substance is not effected in the stomach, 

 it is evident that it cannot be attributed to the saliva or gastric juice ; 

 if the digestion is still effected in the intestinal canal after ligature of 

 the bile-duct, it cannot be attributed to the action of the saliva, gas- 

 tric juice or bile ; if it still go on after ligature of the bile and pan- 

 creatic ducts, the digestive power must of necessity be referred to the 

 action of the intestinal mucus, provided no change has previously tak- 

 en place in the stomach ; but if the food passes unchanged after cut- 

 ting off the supply of bile and pancreatic juice, but proceeds after lig- 

 ature of the bile-duct alone, the act of digestion must be referred to 

 the pancreatic juice. 



The author tirst briefly describes the structure of the starches and 

 starch-containing vegetables employed in his experiments; then the 

 changes produced by cooking, and finally enters on a minute descrip- 

 tion of the changes observed in the experiments he performed on nor- 

 mal digestion, and after cutting off the supply of bile and pancreatic 

 juice. 



The correct appreciation of the structure of the starch-granule is of 

 considerable importauce in relation to these investigations, and the au- 

 thor believes that he has been .able to afford a satisfactory solution of 

 these vexed questions. The changes observed during the digestion of 

 starch favour the original opinion of Leuwenhoeck, that the starch- 

 granule consists essentially of an investing membrane or cell-wall, en- 

 closing an amorphous matter, the true starch, which strikes an intense 

 blue colour with iodine ; and these changes also support the opinion of 

 Professor Quekett, that the concentric circles seen on the starch-gra- 

 nules of man}' plants are simple foldings of the investing raend^rane, 

 leaving it still doubtful, however, whether these concentric circles are 

 not in the starches of some plants composed of linear series of dotted 

 elevations or depressions of the investing membrane. 



* The London, Edin. and Dub. Phil. Mag. 



